An in-mold decoration (hereinafter simply referred to as “IMD”) process includes disposing a decoration film made of a base sheet and a decoration layer provided thereon, between a fixed mold and a movable mold of an IMD molding die, and injecting a molding resin into a molding space defined by clamping the fixed mold and the movable mold, so as to form an injection-molded product and to integrally adhere the decoration layer to a surface of the injection-molded product at a time. Recently, the progress in designing capability and the requirement for higher physical properties from a molten resin surface are aggressively promoting the development of the two-sides IMD process for providing a decoration not only on one side but on both sides of the injection-molded product, as disclosed in JP-A Laid Open No.H06-99457.
According to the two-sides IMD process, two sheets of decoration films are placed between the molds, and upon clamping the molds a molten resin is injected into a cavity defined by the molds. At this stage, the molten resin should be injected into between the two decoration films, and hence an area where the two decoration films are not overlapping have to be secured. Accordingly, as shown in FIG. 17, the decoration film 100 is disposed on the side of a movable mold 201 so as to move lengthwise, while the decoration film 110 is disposed on the side of a fixed mold 202 so as to move laterally, so that a molten resin can be injected from a sprue 254 located at a position where the two decoration films 100, 110 are not overlapping, thus to be supplied into a molding space defined by cavities 228, 258 through a runner 256.
In the two-sides IMD process, when the molds are clamped, inserts 220, 250 tightly hold the decoration films 100, 110 therebetween, thus to keep the decoration films from stretching freely. This causes the decoration film to be wrinkled or torn during the injection-molding process. To avoid such problem, both of the fixed mold and the movable mold of the two-sides IMD molding die are provided with a predetermined clearance A to secure a passage for the decoration films 100, 110 (Ref. FIG. 18A). The clearance A has a dimension substantially the same as the thickness of the two decoration films, so as to avoid imposing the clamping pressure on the decoration films.